The present invention relates to a system for controlling the clutch current of an electromagnetic clutch disposed between a crankshaft of an engine and a transmission of a motor vehicle.
Clutch current flowing in a coil of the electromagnetic clutch increases with an increase of the engine speed for starting the vehicle. When vehicle speed exceeds a predetermined speed (for example 20 km/h), a lock-up current flows through the coil, so that the clutch is entirely engaged.
Change speed gears in the transmission can be manually changed by cutting off the clutch current. Accordingly, a vehicle provided with such an electromagnetic clutch is not provided with a clutch pedal. For cutting off of the clutch current, a shift lever switch is attached on a gear shift lever and a neutral switch which is closed at a neutral position of the gear shift lever is also provided. When the shift lever switch is manually operated and the gear shift lever is operated for changing gears, the clutch current is cut off during the operation of the lever.
In such a system, if the shift lever switch is not properly operated during the change-speed operation, which is usually caused by incorrect or insufficient manipulation by the driver, the gears can not be changed because of the engagement of the clutch.